Transferring personnel and cargo from ship to ship or ship to shore has always been a difficult procedure because of the inherent motion of the ocean. The continuous motion of the water causes complex movements between the ships, or between the ship and shore, and thus creates problems when it is desired to transfer fragile cargo, such as wounded personnel, from a ship. Safe transfer of personnel between ships is particularly important for hospital ships where injured individuals must be transferred from a transport ship to a hospital ship in high seas.
Prior litter transport systems for ships have generally comprised a boom with a winch line connected to a litter carrier. Smooth take-off and landing for those prior systems has been extremely difficult to achieve even with skilled litter transport operators. Unless the litter carrier is lifted at substantially the peak of the upward movement of the vessel, there is a risk that after lift-off, the vessel will move upwardly and crash into the bottom of the litter. The same problem occurs in attempting to place the litter on the deck of the second receiving vessel, since a sudden upward movement of the vessel may cause a jarring impact which may damage the litter carrier or the patients.